Antenna



Oct. 25, 1932. N, UNDENBLAD 1,884,006

ANTENNA Filed Sept. 7. 1928 4 Sheets-Sheet 1 INVENTOR NIL; E. uymo BY WWW ATTORNEY 1932- N. E. LINDENBLAD 1,884,006

ANTENNA Filed Sept. 7, 1928 4 Sheets-Sheet 2 INVENTOR (9 20 NILS E. LINDENBLAD TTORNEY Oct. 25, 1932. N. E. LINDENBLAD u ANTENNA 4 Sheets-Sheet 3 Filed Sept. 7. 1928 INVENTOR sNji E. LINDENBUD BY A TORNEY Oct. 25, 1932. UNDENBLAD 1,884,006

ANTENNA Filed Sept. 7, 1928 4 Sheets-Sheet 4 INVENTOR N 5 LUNDENBLAD .5 01 flofw A ORNEY Patented Oct. 25, 1932 UNITED STATES PATENT OFFICE NILS E. LINDEN BLAD, OI ROCKY POINT, NEW YORK, ASBIGNOR TO RADIO CORPORATION OI AMERICA, A CORPORATION OF DELAWARE ANTENNA Application filed September 7, 1928. Serial No. 804,445.

This invention relates to antennae, and more particularly to directional antennae for the propagation or reception of short wave Signals.

Several types of beam and projector antenna systems for short waves have been developed, but these are rather complicated in structure and therefore relatively expensive to erect and adjust, and also are structurally suitable only for the wave length for which they have been designed and built. It is the primary object of my invention to provide a simplified antenna which will be capable of accommodating a broad range of wave lengths, and to this end I have experimented very extensively with the problem of radiationfrom transmission lines, as a result of which I have devised an antenna consisting merely of simple linear conductors. The antenna is suitable both for transmission and reception, but for simplification I shall refer to transmission in'the description which follows. Identical structure and theory may be ap lied to reception.

f a standing wave is caused on a linear conductor which is long, relative to the workin wave length, the conductor may be consi ered as composed of successive half wave length linear oscillators connected end to end, in which case there will be no summation of energy nor radiation in an end-on direction because each of the half wave oscillators does not radiate along its axis. Furthermore, there is no radiation at right angles to the wire because although each half wave length oscillator might tend to radiate in this direction, the successive half wave length radiators are opposed in phase, so that at a distance from the wire the average effect is zero. However, there is radiation in a direction intermedlate the normal and longitudinal directions, and with a single conductor, this radiation takes place in the form of hollow cones having common axes in the wire.

This is wasteful of energy, and one object of my invention is to reduce the .conical radi-.

ation so that it will consist only of concentrated lobes having axes in one plane. This ls-accomplished by providing two collaterally spaced substantially parallel linear conductors which are long, relative to the workng wave length, and which are coupled in phase opposition. Because of the opposed I phase relation in the two conductors there is substantially no radiation normal to the plane of the conductors, that is, by spacing them apart the radiation from the pair of conductors is concentrated, essentially, into conjugate pairs of oppositely directed'lobes the axes of which lie in the plane of the conductors.

This arrangement, too, is wasteful of energy, and it is a further object of my invention to strengthen the radiation in one pair of opposite critical directions, while weakening the radiation in the conju ate pair of opposite critical directions, which I do by staggering the pair of wires, longitudinally, so that their ends make an angle with the transverse axis of the antenna equal to the critical angle of radiation, that is, the angle which the principal lobes of the radiation pattern of the antenna make with the longitudinal axis of the antenna. In this manner radiation in one pair of opposite directions from each of the conductors come on the same wave front at the same time, but being opposite in phase, they neutralize and cancel each other. In the conjugate directions, owing to the physical displacement of the conductors, the radiated energy tends to add. To make this addition a maximum it is desirable that the added energies be combined exactly in phase, and to provide for this the spacing of the pair of wires should be such that their distance apart, measured in the direction of radiation, is an odd number of half wave lengths.

The radiation has so far been reduced to a bidirectional radiation, and a further object of my invention is to make it unidirective, for which purpose I provide another pair of simple linear conductors arranged to form another antenna such as I have already described, spaced apart from the first antenna an odd number of quarter wavelengths in the direction of desired propagation, and energized in phase quadrature so that the entire system "is made unidirective.

Instead of forced feeding of energy to the second antenna a ure reflector action may be employed, in w ich case only one of the pairs of conductors is energized, m the case of a transmitterforponnected to the receivin set, in the case of a receiver, wh1le the ot er pair of conductors is properly tuned and spaced and staggered so as to provide reflector action by reason of the energy transferred thereto from the other pair of conductors.

It has already been mentioned that .the use of a pair of conductors causes the radiation to lie more nearly in a single plane, and 1n order to improve this characteristic a number of stories of antennae, such as I have already described, may be employed, each antenna consisting of conductors lying in a single plane, while the various antennae lie in vertically spaced parallel planes, and are coupled together so as to operate electrically in parallel. The spacing of these planes may be any spacing desired, particularly if a large number is used, but should preferably be a half wave length especially when only two antennae are use To sharpen the directivity in azimuth a number of antenna: may be used which are spaced apart in a horizontal direction, so as to present a broadside array.

A further object of my invention is to elevate the pro agated wave, and this may be done either y arranging the antenna system with the linear conductors spaced apart in a horizontal direction, but with their plane tilted upwards in the'direction of desired propagation, or by arranging all of the conductors so that they lie in a vertical plane, and are spaced apart vertically, and either lie horizontally in said plane, or at such an angle with the horizontal that the wave is propagated at the desired elevation. To then sharpen the directivity in azimuth a number of such antennae lying in horizontally spaced vertical planes may be used.

The invention is described more in detail in the following specification, which is accompanied by drawings in which Figures 1 and 2 are explanatory of my invention;

Figure 3 represents my antenna in simplest form; v V

Figure 4 represents a bidirective antenna constructed in accordance with my invention;

Figure 5 is a unidirective antenna employin an energized reflector;

igure 6 1s a unidirective antenna employing a tuned reflector;

Figure 7 is a modification of Fig. 5;

Figure 8 indicates schematically an antenna system employing a plurality of antennae spaced vertically and horizontally to increase directivity in elevation and in azimuth, respectively;

Figure 9 is a schematic representation of an antenna and reflector lying in a vertical plane to obtain elevated radiation; and

Figure 10 indicates schematically a broadside aray of antennae lying in vertical planes to increase the directivity in azimuth. In Figure 1 there is shown a simple linear conductor 2 a half wave in length. The

maximum radiation from this conductor takes place normally of the conductor, the attern, in section, being a figure 8 such as is indicated by the lobes 4 and 6.

When a conductor which is long, relative to the wave length, is employed, and a standing wave is caused thereon, the radiation nor-.

mal of the conductor is opposed in phase in the successive half wave length portions of the conductor, and consequently there is no radiation normally of the wire. There is no radiation endwise of the wire because although in this direction radiated energy would add favorably, there is no radiated energy to be added. The radiation takes place in an intermediate direction, and the principal rediation is indicated in Figure 2, in which there is a long conductor 8, on which a standing wave is caused, and from this conductor radiation takes place in conical lobes, such as the lobes 10 and 12. It will be seen from the figure that these lobes are in the form of hollow cones having their apices adjacent and located in the conductor. In actual practice it should be kept in mind that there will be a number of different cones of various lesser magnitudes, and lying in different directions, relative to the longitudinal axis of the antenna, but for the sake of simplicity only the rincipal radiation is indicated, and its direction is indicated by the angle a. 4

Referring to Figure 3 it will be seen that there are a pair of long conductors 14 and 16, and that these are substantially parallel and collaterally spaced. The conductors are connected in phase opposition to the transmitter 20 through tuning reactances 22, the latter being adjusted to cause standing waves on the conductors 14 and 16 by making the total electrical length of the circuit around the two wires a whole number of half wave lengths. This number should be odd, in order that the open ends of the conductors may be opposite in polarity. It should be noticed that these wires preferably are left with open ends, as a simple expedient to favor the growth of standing waves. If the transmission line 24 which interconnects the transmitter and the antenna is long, so that standing waves thereon might tend to cause undesired radiation, the transmission line may be closed with an impedance matching device 26, so that standing waves exist only between the device 26 and the antenna, and not on the line 24.

In a direction normal to the plane of the conductors 14 and 16 radiation is cancelled because of the phase opposition of the energy 2 are reduced to four e in the conductors, and consequently the hollow cones of radiation indicated in Fi or lobes, the axes of which lie in the plane of the conductors. These lobes ma be grouped into the oppositely directed obes 30 and 32, and a conjugate pair of oppositely directed lobes 34 and 36. The, direction of radiation here also makes an angle a with the longitudinal axis of the antenna. I

Referring to Figure 4 it will be seen that the arrangement there disclosed is quite similar to that shown in Figure 3 except that the conductors 14 and 16 have been stag ered, longitudinally, so that their ends ma e an angle on with the transverse axisof the'antenna. This causes the radiation corresponding-to the lobes 34 and 36 .in Figure 3 to come on the same wave front at the same 20 time, and being opposed in phase, the radiation is lpractically cancelled, making the antenna idirective, in the direction of the lobes 30 and 32, which are correspondingly strengthened, for radiation in this direction is additive, owin to the displacement of the conductors. he transverse spacing of the conductors is indicated by the dimension D, and should-be such, preferably, that when multiplied by the cosecant of the an 1e so of radiation or, the product will e ual an o d wave len the antenna will be effectually prenumber of half wave lengths, or in this case the radiation from the two conductors will combine exa'ctl in phase. It'is slightly desirable, but not essential, that the spacing D be one or more wholes, in which case radiation transversel o vented; but this condition can only be met for certain special cases of the angle a, and is not important, owing to the fact that each wire is essentially non-radiative in a normal direction.

Referring now to Figure 5 it will that there are two pairs of collaterally. spaced conductors, 14, 16 and 114, 116, and each of these pairs is arranged in accordance with the principles set forth in connection, with V Figure 4. The pairs of antennas are'enerrather than a len being introdu bythergcant of them le of princif I6 'gized in IEaargrllel through a branched transmission e system, and the feed is made such that the antennae are energized in phase quadrature. This may be obtained most simply by having the arms of the branched traon l 1 ne difier in length by an odd number of quarter wave lengths, as has been indicated in the drawin t is difference in ahead of the imance matching devices, so that it exists in lines on which there is a travl%ling wave wave. e pairs of conductors are apart a distance d and this distance is such thatw'hen multi lied dlation a, theproduct be an od number of quarter wave-lengths, so that owing be seen to t to the initial phase difl'erence'in the energization of the antennae, the radiated ener in one of the opposite directions, as 30, ad 5, I I

while in the opposite direction the energies are opposed, and cancel, thereby making the antenna unidirective, instead of bidirective.

Thearrangement shown in Figure 5 employs an energized or forced feed reflector,

which maybecalled a director, but it is.

also possible to use a simple tuned reflector energized from the other air of conductors. In this case it is desirab e to have the reflector near the energized'conductors, and in such case the arrangement preferably is slightly modified as in Figure 6, in which are staggered so as to make an angle a with the transverse axis of the antenna, and the same applies tothe reflecting conductors 214- and 216. Also, as before, thedistance D is so chosen that when mult' lied by the cosecant of the angle aHthe product will equal an oddnumber of half wav lengths, so that radiation in the direction 0 stagger will be added as nearly as possible in phase, and

furthermore, the distance D may, if desired,

be made one or more whole wave lengths. The conductors 14 and 16 are energized in phase opposition from a transmitter 20, and if desired, an imped nce matching device 26, and tuning means 2, may be employed. The conductors 214 and 216 are coupled in phase opposition, and are provided with a tuning eans 222, here illustrated as a trombone slide, so that the reflector may be tuned to favor the production of standing waves.

The problem of the spacing and of the 'sta ger of the reflector conductors, relative as in the precedin case. If ener induced in the con uctor 216, from e conductor 16, only along the line of direction e conductors 14 and 16, is not so simple were of principal radiation, as indicated by the dotted arrow 40, the rule would be to make this distance a quarter wave, so that the reflected energy would combine in phase with the ener y radiated from the conductor 16 inone irection, and out of phase in the opposite direction. The situation is com licatedby the fact that energy is induce inthe conductor 216 from the conductor 16 along the shorter normal path, indicated b the arrow 42', and from the. conductor-.1 indicated by the arrow 44, so that thrzahase and magnitude of the current in the actor is the resultant of several factors. The best arrangement may be found by experiment, and stated in ageneral fash on, the rule is that the spacing and should be such that the efl'ective electr cal spacmg'j is a quarter wave, while the i 114, 116, as in Fig. 5,

' cover a great wavelength range, because the adjustment can be made for a difi'erent number of half waves in length, whenever necessary to accommodate a desired wave length. The transmitter is coupled to the antenme through a transmission line 24, which is coupled to the trombone slide 46 at points so spaced that the impedance of the line is matchedm The trombones 46 are interconnected by a line 90, the ends of which are coupled to the trombone slides at points so spaced that the impedance of the line is matched, so that there is a travelling rather 5 than a standing wave on the line. In this manner the line may be used to introduce a phase change, and is made one, three or five etcJ, quarter waves in length to obtain phase quadrature in the antennae. Three meters,

39 92, are inserted along a quarter wave porlel through a vthe ra plane, is schematicall in tion of the line, and are made to read alike "when'the line is properly adjusted.

The conductors 114 and 116 are lengthened by the addition of the loops 94 and 96, so as {5' to equal the conductors 14 and 16 in length.

With this precaution the antennae should both take equal current. Ammeters 98, shunted to the trombone slides 46, are made to read alike, and at a maximum, when the antenna is properly adjusted.

In connection with Figure 3, and the succeeding figures, it has been pointed out that iation takes place principally in the plane of the conductors, and in order to sharpen this characteristic antennae, .such as have already been described, may be located above one another in parallel planes, so as to make a multi 1e storied antenna. This has been indicate in A, of Figure 8, in which an entire antenna, consisting of a pair of conductors, and either an energized or non-energized pairof reflecting conductors, properly staggered, and 1 ing in a single icated by the U shaped line 50. Anot er such antenna sys tem, lying in a parallel plane, is indicated at 52, and these are fed electrically in paralbranched transmission line system, schematically indicated by the single lines 54, 56 and 58. The spacing should preferabl be a half or odd number of half wave lengt so as to provide complete cancellation in an up and down direction. With this type of antenna the structure is arranged at an angle a, in azlmuth, relative to the fed cophasially,

direction in which radiation is desired. If it is desired to sharpen the directivity in this direction, i. e. in azimuth, a plurality of antennae may be arranged in broadside, and

I as is indicated by the antenna systemstA and B in Fig. 8. If elevated radiation is desired, the planes in which each antenna lies must be correspondingly tilted or elevated away from a truly horizontal direction. The antennae so far described provide horizontal polarization.

By positioning the plane of an antenna consisting of two pairs of conductors, such as has already been described in connection with Fi ures 5, 6, and 7, in a vertical plane, as is indicated in Figure 9, radiation with vertical polarization may be provided. In this case the antenna is directed in the direction of desired propagation in azimuth, and the angle or provides the angle of elevation. This arrangement is desirable because the elevated radiation is obtained without the expense of an elaborate supporting structure for holding the antenna at the corresponding angle. Slight changes in the angle of elevation may be made by slightly changing the position of the conductors, relative to the horizontal, while keeping them in a vertical plane.

In order to sharpen the directivity in azimuth a number of antennae, located in parallel planes, may be provided as has been indicated in Figure 10, in which each of the an-' tennae 70, 72, and 74 is an antenna such as has been described in either of Figures 5, 6, or 7, and the various antenna: areenergized electrically in parallel through a branched transmission line system 76, 78, 80. The branches are so arranged that the antennae are energized cophasially, and they are preferably spaced a half wave apart, but may be at any spacing, especially when a considerable number antennae are employed. This antenna system propagates a vertically polarized elevated wave.

Over a considerable range of tuning the angle (1 remains quite constant. Only by changing the wave length so greatly that the character of the long wire is completely changed so as tobe a. relatively few instead of many waves in length, does that lobe of radiation which is greatest in magnitude shift or Igump from one to another,-so as to definite and considerably change the angle of radiation 41. For example, using conductors aplproximately eight mean waves in length have varied the tuning from about five to seven meters without appreciably changing the angle of radiation. The antenna is tuned, but the antenna structure itself need not be changed. The tuning is small in' amount because it is needed only to bring the total electrical length to the nearest odd number of half waves, rather than to a fixed length.

I claim:

- 1. A directional antenna comprising a collaterally s aced pair of simple linear conductors a apted to have standing waves formed thereon which are long, relative to the working wave length, and means energizing'said conductors in pgase opposition at adjacent ends of said con uctors, said conductors lying on the same. side .as said energizing means and extending away from said energizin means whereby radiant action occurs pre ominahitly in a direction making equal angles greater than zero degrees with reference to said conductors.

, 2. A directional antenna comprising a collaterally s aced pair of substantially are allel simp e linear" conductors adapted to have standing waves formed thereon which are long, relative to the working wave length, and means energizin said conductors in phase opposition, sai

one side of and extending away from said energizing means, radiant action occurring predominantly in a direction making equal angles greater than zero degrees with reference to said nductors. r

3. A'directional antenna comprising a collaterally spaced pair of substantially paral-- lel simple linear conductors which are long, relative torthe working wave length, means I 7 coupling said conductors in phase opposition,

and means for tuning said' conductors and coupling means to an overall electrical length of an odd number of half waves, so as to cause standing waves of oppositepolarity on' the conductors.

4. A directional antenna comprising a collaterally spaced pair of simple linear con-' 'ductors which are long, relative to the working wave length, and which are so staggered longitudinally, that radiation in one pair oi opposite critical directions' is strengthened, while radiation in the conjugate air of opposite critical directions is wea ened, and

means coupling said wires in phase opposition. a s

5. A directional antenna comprising acollaterally spaced pair of substantially parallel simple linear conductors which are long, rel- V ative to the working wave len h, and which 1 are so staggered, longitudinal y, that radiation in onepair of opgsite'critlcal directions is strengthened, whi e radiation in the conn jugate pair of opposite critical directions is 5 weakened, means cou ling said conductors in I phase opposition, an means .for tuning. said conductors and con ling means to an overall *electrical length 0 an odd number of half waves, so as to cause standing waves of oppoqp site polarity on the conductors.

6. A directional antenna comprisin conductors all lyin in the same plane, the conductors ineach 0 said, airsof conductors es being long, relative to t 'e working wave conductors lying on the antenna unidirective, and means couplintfi two pairs of collaterally spaced simple inea'r" po it cr ti a 4 pairs of conductors being so stage and 130 ing two pairs of collaterallyigpaced and substantially parallel simple earconductors all lying in the same plane, each conductor being longfrelative to the working wave length, the conductors in each pair being so staggered, longitudinally that radiation in one pair of opposite critical directions is strengthened, while radiation in the conju- 8 gate pair of opposite critical directions isweakened, means coupling the conductors in each pair in phase oppositlon, means for tuningtsaid conductors and coupling means to an overall electrical length of an odd number of half waves; so as to cause standing waves of opposite polarity on the'conductors in each pair, said pairs of conductors being so spaced apart in the direction of radiation as to makethe antenna uni I and means coupling at least one ofthe pairs of conductors with radio equipment; 8. A directional antenna system-comprise ing two pairs of collaterally s aced and subgi'incipal stantially horizontally'paralle simple linear conductors all lying m the same vertical plane, each conductor bein long relative to the working wave length, 1: e conductors in each pair being so staggered, longitudinally, that radiation 1n one an of opposite critical directions is strengt ened, while radiation in the conjugate pair of opposite critical directions is weakened, means the conductors in each pair in phase opposition, means for tuning'said conductors and cou- 'pling means to an overall electrical length? of an odd number of'half' waves, so as to cause standing waves of opposite. polarity on the conductorsin each air, said pairs of conductors bein so space a art in the direction of desire radiant action as to make at least one of the pairs of conductors radio 'equipment.-

critical-directions is strengthened,

while radiation in theconjugate air of op directions is wea ened said rective,

- I 9 9. A directive transmission. system com-" spaced apart in the direction of principal radiation as to make the antenna unidirectional, means coupling the pairs of conductors in phase opposition, a radio transmitter forenergizing the conductors, and means coupling the transmitter to at least one of the pairs of conductors in phase opposition.

10. A directive transmission system comprising two pairs of collaterally spaced and substantially parallel simple linear conductors all lying in the same plane, each conductor being long, relative to the working wave length, the conductors in each pair being so staggered, longitudinally, that radiation in one pair of opposite critical directions is strengthened, while radiation in-the conjugate pair of opposite critical directions is weakened, means coupling the conductors in each pair in phase opposition, means for tuning said conductors and coupling means to an overall electrical length of an odd number of half waves, so as to cause standing waves of opposite polarity on the conduc-- tors in each pair, said pairs of conductors being so spaced apart in the direction of principal radiation as to make the antenna unidirective a radio transmitter for energizing the conductors, and means coupling the transmitter to said pairs of conductors in phase quadrature.

11. A directional antenna system including a plurality of unidirectional antennae lying in spaced parallel planes, each antenna comprising two pairs of,co1laterally spaced and substantially parallel simple linear conductors lying in a single plane, the conductors being long, relative to the working wave length, the conductorsin each of said pairs being so staggered, longitudinally, that radiation in one pair of opposite critical directions is strengthened, while radiation in the conjugate pair of opposite critical directions is weakened, means coupling the conductors in each pair in' tuning said con uctors and couplin means to an overall electrical length ofan d number of half waves, so as .to cause standing waves of opposite polarity on the conductors in each pa1r, said pairs of conductors being 0 so staggered and spaced apart in the direction of principal radiation as to make the antenna unidirectional, and means coupling corresponding pairs of conductors in each of the antennae in parallel and in proper phase 66 to radio equi ment.

12. A uni irectional antenna system including a plurality of unidirectional antennae lying in spaced parallel vertical planes, each antenna comprising two pairs of collaterally spaced and substantially horizontal parallel simple linear conductors lying in a single lane, said planes being spaced transverse y of the antenna so as to sharpen the directivity in azimuth, the conductors 06- being long relative to the working wave hase opposition, means for antenna unidirectional, and means coupling length, the conductors in each of said pairs being so staggered, longitudinally, that radiation in one pair of op osite critical directions is strengthened, w ile radiation in the conjugate pair of opposite criticaldirections is weakened, means coupling the conductors in each pair in phase opposition, means for tuning said conductors and couplin means to an overall electrical length of an o d number of half'waves, so as to cause standing waves of opposite polarity on the conductors in each pair, said pairs of conductors being so staggered and spaced apart in the direction of principal radiation as to make the corresponding pairs of conductors in each of the antennae in parallel and in proper phase to radio equipment.

13. A directive transmission system including a plurality of unidirective antennae lying in spaced parallel planes, each antenna comprising two pairs of collaterally spaced and substantially parallel simple linear conductors lying in a single plane, the conductors being long, relative to the workin wave length, the conductors in each of sai pairs being so staggered, longitudinally, that radiation in one pair of opposite critical directions is strengthened, while radiation in the conjugate pair of opposite critical directions is weakened, means coupling the conductors in each pair in hase opposition, means for tuning said con uctors and coupling means to an overallelectric'al length of an odd number of half waves,so as to cause standing waves of opposite olarity on the conductors in each pair, sai pairs of conductors being so staggered and spaced apart in the direction of principal radiation as to make the antenna unidirectional, a radio trans-. mitter for energizing said antennae andmeans couplin corres onding pairs of conductors in sac of said antennae in parallel and in roper phase to the radio transmitter.

14. unidirectional short wave antenna 11 comprising four collaterally spaced substantially parallel wires which are long, relative to the working wave length, all lying in a single plane, means for coupling pairs of the wires in phase opposition, means for tun- 115 ing the pairs of wires to an odd number of half waves in total electrical length so as to cause standing waves of opposite polarity. thereon, the wires in each pair bein stag- I geredlongitudinally so that their en s form I the same angle, relative to the transverse axis of the antenna, that the direction of principal radiation makes with the long tudinalaxis of the antenna, and spaced apart an odd number of half wave len direction of-principal radiation, t e pairs of conductors being so staggered and spaced apart that energy from one pair combines with the energy from the other pair in base so 'as to ma e the antenna unidirectional, 130

hsin-the gi I single'plane, a pair of trombone sli es for neeaooe and radio equi ent coupled to at least one of the pairs conductors.

15. A unidirectional short wave antenna co'mprising four collaterally spaced substantially parallel wires which are long, relative to the working wave length, all lyin in a' together pairs of the wires and for tumng t em to an odd number of half waves in total electrical length so as to cause standlgwaves of opposite polarity thereon, the wires in each-pair being staggered longitudinally so that their ends form' the same angle, relative to the transverse axis of the 1 antenna, that the direction of principal radiation makes with-the longitudinal axis of the antenna, and spaced apart an odd number of half wave lengths in the direction of principal radiation, the pairs of conducao tors bein spaced aparta quarter wave length in the 'rection of principal radiation, a

transmission line a quarter wave in length coupled to the trombone slides at points so spaced that the impedance therebetween matches the impedance of the transmission line, and radio exflui ment coupled to one of the trombone s id es. V y

.16. The method of securing unidirectional electro magnetic wave propagation which includes producing a standing wave, producing another physically shifted standing wave of o posite polarity, and combining the fields pro ticed by the standing waves whereby propagation of electro-magnetic energy is unidirectional. I I

'17. A directional antenna comprising a collateral] spaced pair of simple'hnear conductors w 'c are long, relative to the working wave length and which are so staggered, longitudinal y that wave action in one pair of opposite crltical directions is strengthened, while wave action in the conjugate pair of opposite critical directions is weakened, andv means for energizing said wires imphase op:

position. T

18. A directional antenna comprising a collaterally spaced pair of simple linear conductors which are long relative to the working wave length, and which are so staggered,

the conjugate pair of opposite critical direclongitudinally, that electromagnetic action in on'epair of op osite critical directions is strengthened, wh' e electromagnetic/action in tions is weakened, said wiresadapted to be energized in phase opposition.

' v 19. A unidirectional antenna comprising A spaced linear conductors, means for causing standing waves of different polarity thereon, said conductors being stag ered whereby ac-, tion of'the antenna is pre ominately unidiiectional.

20. A directional antenna comprising a collaterally spaced pair of substantially parallel simple linear conductors which are long, relative to the working wave length, and which v v v are so staggered, longitudinally, that wave action in one pair of opposite critical direcfor actionally couplin the conductors, and

means for tuning sai conductors and cou-' pling means to an overall electricallength of an odd number of half waves, so as to cause standing waves of opposite polarity on the conductors. a

21. A directional antenna comprisin two pairs of. collaterally spaced simple near conductors all lying in the same plane, the conductors in each of said airsof conductors being long, relative to t e workin wave length, and so staggered, longitudinal y, that electro-magnetic action in one pair of 'opposite critical directions is strengthened, while electro-magnetic action in the conjugate pair of oppgsite critical directions is weakened, said pa rs of conductors bein so staggered and spaced apart in the direction of rincipal e ectro-magnetic action as to ma e the antenna unidirectional, eans coupling the pairs of conductors in p ase opposition, and means coupling at least one of the pairs of conductors with/radio equipment.

22. A directional antenna system comprising two pairs of collaterall spaced and substantially parallel simple ear conductors all lying in the same plane, each conductor being long, relative to the working wave length, the conductors in each pair being so staggered, longitudinally, that radiant action in one pair of opposite critical directlons is strengthened, w ile radiant action'in the cdnjugate pair of opposite critical directions is weakened, means coupling the conductors in. each pair in phase opposition, means, or tuning said conductors and coupling I pair of long linear wires connected at ad- Lacent ends to high frequency apparatus and avmg standing waves of op osite instan-' taneous polarity thereon, sai wires being several wave lengths in length and extending away from and on one side only of said adjacent ends.

24, A directional antenna system comprising a pair of'long straight wires and means at adjacent ends of the wires for exciting the 'wires in phase opposition whereby standing waves of opposite instantaneous polarity are set up on, the wires, 'said wires being several wave lengths in length at the operating frequency and extending on one side only and away from said adjacent ends.

25. A directive antenna system for propagating or receiving propagated electromagnetic waves comprising a pair of substantially straight conductors, long, relative to the working wavelength such that several standing waves at the operatin frequency are set up on each conductor, sai conductors being arranged so that radiant action occurs in a direction making the same angle with each conductor, and means couplin said conductors in phase opposition, sai conductors lying in the same plane and extendin away from said coupling means on one si e only thereof.

26. A directive antenna system for propagatin or receiving electromagnetic waves as claime in claim wherein a similar pair of conductors are provided, the conductors of said similar pair being arranged parallel to the respective conductors of the first pair I whereby the directional efiect of the system 25 is augmented.

27. A directive antenna system for propagatin or receiving electromagnetic waves as clalmed in claim 25 wherein a similar pair of conductors are rovided, the conductors of said similar pair Ewing arranged parallel to the respective conductors of the first pair and 1 ing m the same plane as the plane of the rst pair whereby the directional efiect of the system is augmented.

8B 28. A directive antenna system for propagating or receiving electromagnetic waves as claimed in claim 25 wherein a similar pair of conductors are provided, the conductors of said similar pair being arranged parallel to the respective conductors of the first pair and 1 'ng in a plane parallel to the plane of said rst pair whereby the directional effect of the system is augmented.

29. A directive antenna "system for propanetic waves, comprisingl a plurality of airs of conductors arrange in the same p ane, respective conductors of the pairs being substantially parallel, each of said conductors being long relative to the working wave length-and adapted to have a plurality of standin waves at the working wave length set up t ereon, means for connecting the conductors of each pair in base opposition, the conductors of eac pair extending on one side only and away from said connecting means, and, a like number of pairs of conductors arran ed in a plane parallel to the plane of said rst mentioned plurality of pairs of conductors, the conductors in the like plurality of vpairs being arranged parallel to the conductors of said first mentioned plurality of pairs, the conductors of said like pairs being coupled and arranged '45 in a manner similar to the conductors of said gating or receiving propagated electromag- ,7

first mentionedpairs of conductors, like conductors of the airs bein arranged in parallel fashion whereby ra iant action occurs predominantly in a direction makinglequal angles greater than zero degrees wit each 7 conductor of said s stem.

NIL E. LINDENBLAD. 

